I'm unsure if any of you have heard of this before, but it works like the regular legacy challenge, with one difference..
You start off with the most ugly sim possible, and after 10 generations see if you have successfully diluted the ugly gene.
Follow regular 10-gen legacy rules. No marrying custom made characters.
Oh, and you can kill off the mother/father (NOT the original heir) of future heirs to make space for more in the family, if you so wish.

Now, of course, everyone will have a different idea of what makes someone (or your Sim) truly ugly, but here is my example.. Pushing body bars to the extremes is always helpful.

Suggested traits to make it harder (or more fun, depending on your play style..)
Clumsy, Coward, Dislikes Children, Insane, Inappropriate, Loser, Loner, Unlucky, Grumpy, Neurotic, Slob, Snob, etc. You may also include one positive trait, such as good, handy, etc.

So, meet Faily McFailton (I know, original.) He's just your regular run-of-the-mill guy.. Well, sort of. He's always found that bad luck follows him, he's a bit of a loser and he's been conditioned to be afraid of anything, and everything, that may hurt him. Unfortunately for him, he's also neurotic, which can lead to bursts of inappropriate behaviour. But hey, not everyone is perfect.. Right? Watch out ladies, his LTW is heartbreaker.

Meet Sicilia. She's a genie! She comes from a long line of genies, who find it gravely important to have "pure" genie blood. Unfortunately, this has led to a great deal of inbreeding, and a family history of morbid obesity, since genies really do not get out much by their very nature.

Sicilia has always been the rebel of the family, though, and a downright non-conformist, even in the clothes she wears. In her bottled state, she was purchased by a rich, snobby widow named Liana Stillbrook, who kept her in the private library of her estate as a collector's item, occasionally calling upon her for the odd beautification or...richification wish. That is, until she was stolen by a kleptomaniac maid named Grady Elfman, who had been cleaning Liana Stillbrook's house when that mysterious sparkling bottle caught his eye.

He took her to his apartment, and popped open the cork. To his great surprise, Sicilia appeared! She gave him the usual "your wish is my command" spiel, and although her wishes were unlimited (none of this three wishes only crap for pure-blood genies!) Her beauty captivated him, and he said he only wanted three things anyway.

"First, I want a new house, instead of this lame apartment. I want it to be simple, and easy to maintain. I don't want anything fancy...just a quaint little home in Sunset Valley."

With a wave of her hands, Sicilia transported him to the Monotone house he'd often passed on the way to Mrs. Stillbrook's! To his amazement, he noticed a piece of paper in his hand. It was the deed to the new house! She still waited before him, anticipating his next wish.

When he had gathered his bearings, he managed to speak his next wish. "Next, I'd like to deviate from my normal routine a little. It's always clean, clean, clean, steal, steal, steal, day after day. It's enough to drive me crazy. Do you think you could manage me a surprise for once?"

"As you wish," Sicilia said mysteriously, baffled at his unusual and unspecific request. She waved her hands and a meteor hit his new house. Sicilia was never good at these kinds of "surprise me!" wishes, unlucky loser as she was.

"Not quite what I expected," said the charred Grady Elfman, "but all right, I guess I can get some nice space rocks out of it." He felt truly disgusted by his surroundings, but the radiant being before him made it all worthwhile.

"Lastly, I wish you were free," said the maid, and lo and behold, Sicilia found herself standing solidly on the ground, no longer trailing ethereally from the bottle! She gave a shout of joy!

"But...now that you're free, I have one last wish. Of course, now, you're not bound to it at all, so you can go ahead and walk away if you don't feel comfortable with it. Sicilia, will you marry me?"

How could she say no to the beautiful man who had freed her so selflessly from her glass prison? "Yes, yes, yes, my Grady!" And she melted him with kisses.

Sicilia knew this would be a great opportunity for her. She always wanted children, but she didn't believe in her parents' insistence that the genie lines must be kept pure. No, it was time for genie geneology to branch out, and even if it meant losing their ability to grant wishes, it was more of a curse than a gift, anyway. And, best of all, maybe one day all the signs of inbreeding and tendency toward obesity would disappear! As Sicilia faintly heard the twinkling of a sweet lullaby in her ear after the first wonderful evening with her new husband came to a close, she knew she was making the right decision for her future children.

Well arent they beutiful. I'm gonna have fun with this one expect one expection.... You must marry the first single person you see(with expections)
That means if the guy is really teribley ugly too bad you have to marry him. This adds a little bit of luck.

Haha, the more I look at that kissing picture I took of Sicilia and Grady, the more I think it looks like he's literally -smothering- her with kisses, and that's why she's blue and her cheeks are so puffed. Makes me laugh. And thanks!

I'll be surprised if I can breed out the "ugly" from Sicilia in one generation. I just downloaded a "prettier" replacement for the blue skintone, but if I have any doubts about the offspring's ugliness, I'll remove it and see what happens.